Azoxystrobin is a broad-spectrum and high-efficient fungicide product used in agriculture, which has the world's largest sales at present and is widely produced and used. Synthesises of compound B and compound C, which are key intermediates of azoxystrobin, are generally performed by a ring-opening and etherification reaction of benzofuranone (compound A) with 4,6-dichloropyrimidine in sodium methoxide/methanol solution.
At present, a majority of domestic enterprises adopt the method as disclosed in CN1062139A, i.e. adding sodium methoxide directly to initiate a ring-opening and etherification reaction and thus synthesizing a mixture of compounds B and C from compound A without adding any catalyst, which has the route as following:

However, the yield of the method disclosed in CN1062139A can only be maintained at about 60-70% and a large number of by-products are produced in this reaction, which directly affects the purification of product in subsequent steps.
Another preparation method is synthesizing a mixture of compound B and compound C from compound A by using the catalyst DABCO as disclosed in CN102311392A. However, such catalyst is expensive, and has a high boiling point and thus is difficult to recycle, resulting in a high ammoniacal nitrogen content in wastewater, difficulties and high costs of wastewater processing and disadvantages for environmental protection and energy saving, although DABCO can improve the reaction rate as a catalyst.
Therefore, a low-cost and high-efficient method for preparing azoxystrobin key intermediate compound B and compound C is desired in the art, in which method the catalyst can be easily recycled and the ammoniacal nitrogen content in wastewater can be reduced.